Funny story, I installed the Ubuntu Kylin theme as discussed here and when I decided I didn't like the "Ubuntu Kylin" theme (mostly because I didn't like the new boot screen & greeter), I removed it...

But now the icons are buggered-up.

Here's what I did to remove the Ubuntu Kylin theme, and also to try to fix the issue (using information I found on Ask Ubuntu)...

Use Unity-Tweak-Tool to reset the icons. It's even mentioned in the original link you posted. Alternatively, there's gsettings way , which is also mentioned by luchonacho's link
– Sergiy KolodyazhnyyJul 16 '16 at 9:32

The gsettings method didn't work, but resetting the appearance settings in Unity Tweak did... I was sure I had already tried to reset the appearance settings in Unity Tweak, but apparently not. Thanks!
– Gregory OperaJul 16 '16 at 10:22